Fig. 3. Distribution of ¹⁴C derived from aged (A) ¹⁴C-isoproturon (IPU), (B) ¹⁴C-monodesmethyl-isoproturon (MDIPU), and (C) ¹⁴C-4-isopropyl-aniline (4IA) in uninoculated soils, showing water-extractable ¹⁴C (checkered), NaOH-extractable ¹⁴C (black), or nonextractable ¹⁴C (white). The numbers on columns indicate the percentage of initially added ¹⁴C. The values are the mean of three replicates except for soil with IPU aged for 131 d, which is the mean of two replicates. The vertical bars indicate ±1 SD of the total recovery of ¹⁴C.